Datasheet

5
LTC3405
3405fa
UU
U
PI FU CTIO S
RUN (Pin 1): Run Control Input. Forcing this pin above
1.5V enables the part. Forcing this pin below 0.3V shuts
down the device. In shutdown, all functions are disabled
drawing <1µA supply current. Do not leave RUN floating.
GND (Pin 2): Ground Pin.
SW (Pin 3): Switch Node Connection to Inductor. This pin
connects to the drains of the internal main and synchro-
nous power MOSFET switches.
V
IN
(Pin 4): Main Supply Pin. Must be closely decoupled
to GND, Pin 2, with a 2.2µF or greater ceramic capacitor.
V
FB
(Pin 5): Feedback Pin. Receives the feedback voltage
from an external resistive divider across the output.
MODE (Pin 6): Mode Select Input. To select pulse skip-
ping mode, tie to V
IN
. Grounding this pin selects Burst
Mode operation. Do not leave this pin floating.
3405 G20
V
OUT
100mV/DIV
AC
COUPLED
I
LOAD
200mA/DIV
I
L
200mA/DIV
40µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 20mA TO 250mA
PULSE SKIPPING MODE
V
OUT
100mV/DIV
AC
COUPLED
I
LOAD
200mA/DIV
I
L
200mA/DIV
3405 G21
40µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 20mA TO 250mA
Burst Mode OPERATION
3405 G22
40µs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 0mA TO 250mA
Burst Mode OPERATION
V
OUT
100mV/DIV
AC
COUPLED
I
LOAD
200mA/DIV
I
L
200mA/DIV
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Load Step Load Step Load Step
(From Figure 1a Except for the Resistive Divider Resistor Values)